Longitudinally-obtained serum samples from chimpanzees in the Dedicated Breeding Program (DBP) will be studied by ELISA to determine the titers of IgG and IgM antibodies to Mycobacterium leprae-specific cell wall phenolic glycolipid-I (PGL-I) antigen and the mycobacterial common cell wall antigen lipoarabinomannan (LAM). The antibody profiles will detect chimpanzees that have been exposed to leprosy, a disease only recently shown to exist among the DBP chimps, and will identify individuals that are likely to have sub-clinical leprosy. These animals will be isolated and studied in more detail. To confirm the presence of M. leprae, sera from chimpanzees testing positive for subclinical leprosy will be studied further by a dot ELISA to identify specific PGL-I antigen and by assaying the sera by ELISA for a newly identified M. leprae-specific 35 Kd cell wall protein antigen. The origin of leprosy in the DBP and epidemiologic relationship between M. leprae exposed/infected animals will be explored using the International Species Information System (ISIS) databank that records all inter- Institutional chimpanzee transfers. Information obtained from the participating Institutions regarding caging arrangements and physical contacts between identified exposed/infected chimps and other breeders will be posure/infection, and epidemiological relationships will be sought by comparing the two sets of longitudinal data. Since leprosy has not been previously recognized among primates other than man (and now, perhaps, sooty mangabey monkeys), the ISIS epidemiologic study will be important in tracing the origin of the disease in the DBP. It is important to determine the prevalence of M. Leprae infection among the breeding chimpanzees since preliminary studies suggest that this species may be more susceptible to naturally-acquired leprosy than might be supposed. Further spread of leprosy among the DBP animals can be halted by identification, isolation and chemotherapy of the exposed individuals.